The invention relates first to a method for determining the air aspirated by an internal combustion engine, in which the air flow rate is detected by an air flow rate meter.
It has long been known that the air flow rate aspirated by an internal combustion engine of a motor vehicle can be detected by means of an air flow rate meter. The air flow rate detected is processed in an engine control unit together with other data relevant to the combustion process, such as the temperature of the intake tube pressure, for calculating injection times and the like.
One problem in such known methods for determining the air aspirated by an internal combustion engine is that in determining the air flow rate, variables that effect the air flow rate are ignored. One such variable that changes the air flow rate is the humidity, for instance. If the ambient air is very humid, the humidity makes the air flow rate detected by the air flow rate meter wrong, because not only the air that can be combusted in the engine but at the same time water vapor that cannot be combusted is detected and thus leads to very disadvantageous changes in emissions values.
It is therefore the object of an invention to refine a method for determining the air aspirated by an internal combustion engine, in such a way that only the air that can be combusted by the engine is precisely detected.
In a method for determining the air aspirated by an internal combustion engine, as described at the outset, this object is attained according to the invention in that simultaneously with the detection of the air flow rate, the humidity is detected by a humidity sensor and evaluated in an evaluation circuit. Additionally detecting and evaluating the humidity of the aspirated air has the particularly great advantage that the flow rate of gaseous water aspirated can be distinguished from the flow rate of the air that can be combusted in the engine. As a result, the control circuit of the engine can be supplied with substantially more-precise initial data, and as a consequence, substantially more-precise load signals and other signals determining the combustion process can be calculated and output.
The humidity of the aspirated air can be detected purely in principle in the most various ways. One advantageous embodiment provides that the humidity is detected in an intake tube of the engine, preferably adjacent to the air flow rate meter. As a result, a very precise determination of the humidity of the aspirated air is possible.
In another highly advantageous embodiment, it is provided that the humidity is detected outside an intake tube of the engine. As a result, the detected moisture in the ambient air can also be used for other vehicle-specific purposes. For instance, it is conceivable that if a certain humidity level is exceeded, the windshield wipers, lights or other equipment is automatically turned on.
Furthermore, it can advantageously be provided that in addition, the intake tube pressure is simultaneously detected and evaluated by the evaluation circuit. This increases the precision of the determination of the aspirated air.
It is preferably provided that the intake tube pressure is detected in the intake tube adjacent to the air flow rate meter.
The invention has the further object of improving a sensor for an internal combustion engine, including an air flow rate meter with a sensor element for detecting the aspirated air flow rate, in such a way that along with the air flow rate, the humidity and/or the intake tube pressure is also detectable in a simple way.
In a sensor for an internal combustion engine, including an air flow rate meter with a sensor element for detecting the aspirated air flow rate, is attained according to the invention.
Such a sensor has the particularly great advantage that along with the air flow rate, its moisture and pressure are not only detected but also already processed in the sensor. By means of such a sensor, because of the evaluation circuit disposed in it, the detected data can advantageously be forwarded to a control circuit over only a few connection lines. Such a sensor is therefore especially suitable for connection to a bus system, which requires only two data lines. Such a sensor can also be very compact in construction.
Thus, in an advantageous embodiment, it is for instance provided that the air flow rate meter or the sensor element and the pressure sensor are micromechanical components. It may be provided that the sensor element of the air flow rate meter and the pressure sensor are disposed on a chip or a chiplike ceramic component, which not only results in an especially small structural form but also in particular assures that both the air flow rate and the humidity are detected at practically the same location. In another advantageous embodiment, it is provided that the air flow rate meter or its sensor element and the pressure sensor are disposed on two chips spaced apart from one another. In that case, the pressure measurement can then be done via a certain predeterminable transit path, for instance inside the air flow rate meter tube.